Excitation and emission processes of Tb in porous anodic alumina

The strong photoluminescence (PL) of porous anodic alumina (PAA) with terbium deposition is reported. PAA, which has a regular pore morphology, is considered an effective template for fabricating luminescent composites. Tb was deposited onto PAA films by immersion in alcoholic solution with terbium chloride followed by heat treatment. The PL spectra demonstrate typical bands of Tb³⁺ corresponding to ⁵D₄ → ⁷F_j (j = 3, 4, 5, 6,) electron transition, with the maximum at 18,360 cm⁻¹ (⁵D₄ → ⁷F₅). The PL mechanism of Tb³⁺ was systematically studied with annealing temperature. The non-radiative relaxation channel is provided by OH hydroxyls at the surface of porous anodic alumina and, after annealing at 900 °C, the PL yield is highly improved. The PL intensity of Tb³⁺ increases with laser power and a saturation phenomenon, associated with the ratio of Tb³⁺ to Tb⁴⁺ ions, is observed at approximately 90 W/cm². Based on a theoretical model, the optical cross-section σ of terbium in PAA is estimated, with a value close to that of other porous materials doped with the rare-earth elements.     

实验室光致电离等离子体中激发过程的研究

光致电离等离子体在宇宙中广泛存在于强辐射场附近. 近年来随着高能量密度实验装置的发展, 在实验室内也能构造出光致电离等离子体. RCF是一个基于The Flexible Atomic Code 数据的针对光致电离等离子体的辐射碰撞模型, 该模型模拟了两个光致电离实验, 其 理论结果中电离态分布和光谱与测量值符合得很好. 在理论模拟中发现, 光致电离等离子体中光致激发和碰撞激发过程对离子态布居和发射光谱都有非常重要的影响. 光致激发过程可以通过将离子激发到双激发态从而间接电离离子; 碰撞激发过程会因为电子将基态离子激发到电离截面小的单激发态而抑制光子对等离子体的电离. 光致激发过程可以加强类锂离子的类氦离子的卫线, 而碰撞激发过程会影响类氦离子谱线的线强之比.     

使用光栅单色仪测量红宝石晶体的吸收和发射光谱

使用WDS-8型光栅单色仪测量了室温下红宝石晶体的吸收光谱和发射光谱.通过该实验,学生在了解光致发光原理及光致发光材料光谱特性的同时,掌握单色仪的使用方法和技巧.     

Er3+-Yb3+共掺碲酸盐玻璃上转换绿光激发过程的研究

根据Er³⁺-Yb³⁺共掺碲酸盐玻璃绿光上转换发光的能级结构和相关跃迁建立的速率方程模型,分析了Er³⁺的⁴S_3/2能级上升特性与⁴I_11/2能级和Yb³⁺的²F_5/2能级的关系.通过模型对实验观测的上升和衰减曲线的拟合,确定速率方程模型的相关参数,计算⁴S_3/2能级粒子数布居趋于稳定时能量传递粒子数与激发态吸收粒子数之比.进一步分析了Er³⁺-Yb³⁺共掺绿光上转换发光的动力学过程. 关键词： 速率方程模型 上转换 3+-Yb³⁺')" href="#">Er³⁺-Yb³⁺ 方波激发     

Magnetic field dependence of red emission intensity of ruby at various temperatures

Application of a magnetic field perpendicular to the c-axis of a thin slice of pink ruby at low temperatures reduces the intensity of R-line and vibronic emission. At field intensity H = 6 kG the loss of vibronic emission exceeds 10%. The decay time decreases by a similar fraction. The method used for studying intensity involves on-off modulation of the field, and digital integration. A function which describes the observed fractional reduction of intensity is $\text{F(H) =}\text{AH}{}^2\text{(1 + BH}{}^2\text{)}$ where A and B are nearly constant below 77 K, but decrease rapidly between 100 K and 200 K. The function can be derived by assuming that radiationless transitions to the ground state occur with probability proportional to H² from low-lying vibronic states of ²E. Thermal excitation from these states to states in the neighborhood of ²T₁ is proposed as the mechanism for quenching the magnetic field effects.     

Photon emission under bombardment of ruby by ions and electrons of medium energies

The characteristics of optical radiation produced under bombardment by ions (1–15 keV) and electrons (100–1000 eV) of a ruby surface are studied. Two broad bands with maxima at 330 and 450 nm attributed to defects of the crystal lattice are discovered in the spectral region of 200 to 800 nm. Characteristic radiation related to radiative relaxation of excited Cr³⁺ ions in the near-surface region of the crystal is observed. The dependence of the radiation intensity on the energy and current density of the bombarding particles is obtained experimentally. The degree of radiation polarization is determined.     

Increasing the directionality of ruby laser emission by adjustment of the external reflectors

It is shown that by increasing the distance between the external mirrors of a ruby laser it is possible to reduce the angle of divergence of the radiation at the expense of energy alone. There is an optimal distance at which the light sum of the axial luminous intensity is maximum.     

Role of pure dephasing in the broadening of zero-phonon emission lines in ruby

A theoretical analysis is made of the homogeneous linewidth of the electronic Raman transition between ē and 2ā excited states of Cr³⁺ observed in optically pumped ruby, in comparison with the widths of the phosphorescence R₁ and R₂ lines. In particular, we consider the phenomenological correlation between the broadening processes of the ē and 2ā levels, implied by the experimental fact that the magnitude of the Raman linewidth is approximately equal to the average, rather than the sum, of the R₁ and R₂ linewidths. The origin of this correlation is shown to be the quenching of pure-dephasing processes, associated with elastic phonon scattering, of the ē ? 2ā transition, while the pure-dephasing rates of the phosphorescence transitions are comparable to the rates of population-relaxation (lifetime-broadening) processes, associated with inelastic phonon scattering.     

Surface damage to ruby laser crystals

Surface damage to ruby laser crystals is investigated. To identify the surfacedamage mechanism, the dependence of the damage threshold on the laser pulse duration is investigated from 300 nsec to 0.4 msec. From this dependence, as well as from the dependence of the damage threshold on the defect content of the surface layer, it is concluded that the damage to the surface of the mechanically worked laser ruby crystals is due to a thermal mechanism. Methods are developed for obtaining, by thermal evaporation of oriented crystals, surfaces with increased endurance to laser damage. Such surfaces have a low light-scattering stability.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 101, pp. 9–30, 1978.